Direct Atomic Absorption Spectrometric Determination of Selenium in Biological Fluids by a Graphite Filter Furnace Atomizer with Carbon Thread

A rapid and simple method was developed for the determination of selenium in biological fluids by direct electrothermal atomic absorption spectroscopy. The operation parameters of a commercial longitude heating furnace combined with a graphite filter furnace, graphite thread (tube-in-tube atomization system), and a Pd–Mg chemical modifier were proposed, and the corresponding analytical characteristics for the determination of Se at concentrations greater than or equal to 0.0025?mg/kg in blood, urine, saliva, and breast milk samples were established. Recovery values of Se with the proposed method varied within 93 to 107% for these matrices. Relative standard deviations for the analysis of certified material were also compatible; values of 5 and 7% were achieved for blood serum and urine, respectively. The relative standard deviation obtained by the proposed method did not exceed 8%, and the total time for Se determination was 5 to 7?min. The novelty of this technique is that it offers an effective tool for removing the interferences from 10 to 20?g/L organic and 1.0 to 1.5?g/L mineral components in the materials and for significantly reducing the background absorption of light caused by their presence.     

Optical Study of Interactions of Glass Beads ER Particles

The amount of ER effect is determined by the difference of dielectric constants of ER particles base liquid.The intensity of ER fluids can be characterized by the interaction of two particles. A double optical tweezers system suitable to study particle interaction is used to measure the particle aggregation time, and it is found that the particle aggregation time is proportional to the square of the electric field. This is the first time to directly measure the interaction of the electric dipoles of ER particles. A method is developed to use high speed CCD in measuring diffusing-wave spectroscopy (DWS), and, for the first time, the auto-correlation functions of nonegordic system of particle structure are measured to study the ER mechanism. Structure response time and force response time are obtained for glass beads ER fluid, and the time variation of characteristic decay times of system correlation functions under different electric fields is also measured. Diffusing coefficients under different fields imply that the interaction is proportional to the square of fields.     

Spectrofluorometric determination of nicardipine,nifedipine and isradipine in pharmaceutical preparations and biological fluids

A simple and highly sensitive spectrofluorometric method was developed for the determination of some 1,4-dihydropyridine compounds namely, nicardipine, nifedipine and isradipine in pharmaceutical preparations and biological fluids. The method is based on the reduction of nicardipine, nifedipine and isradipine with Zn/HCl and measuring the fluorescence intensity obtained (λ_em/λ_ex) at 460/364, 450/393 and 446/360 nm, respectively. The factors affecting the development of the fluorophore and its stability were studied and optimized. The effect of some surfactants such as β-cyclodextrin (βCD), carboxymethylcelullose (CMC), sodium dodecyl sulphate (SDS) and triton X-100, on the fluorescence intensity was studied. The fluorescence intensity-concentration plots of nicardipine, nifedipine and isradipine were rectilinear over the ranges 0.4–6.0, 0.2–4.0 and 0.1–9.0 μg ml⁻¹ with detection limits of 0.0028, 0.017 and 0.016 μg ml⁻¹, respectively. The proposed method was successfully applied to commercial tablets containing the compounds; the percentage recovery agreed well with those obtained using the official methods. The method was further extended to the in vitro determination of the compounds in spiked human plasma and urine samples. A proposal of the reduction reaction pathway was postulated.      

Homogenization Efficiency of Two Immiscible Fluids in Static Mixer Using Droplet Tracking Technique

Comprehensive understanding of the mechanism of two-phase flow agitation is essential to control the mixing performance in chemical processes. The aim of the present study is to understand mixing behavior of two phase flow emulsification process in details by utilizing a three-dimensional computational fluid dynamics (CFD) scheme and predicting the flow characteristics of O/W emulsion in a Kenics static mixer (KSM) operating as an in line continuous homogenizer. The overall study is carried out in three steps: (a) a turbulent flow analysis, to obtain an overall characteristic of the emulsion resulting in CFD model and (b) comparing theoretical data of model with those of experimental studies in order to validate the CFD approach; (c) a droplet tracking step, to extensively study the distribution of marked droplets during the mixing procedure. To achieve this goal, the individual droplets being numerically labeled and visually colored regarding their droplet size; a quantitatively scrutiny of mixing for the droplet distribution was introduced. As a result, the droplet tracking using CFD has successfully evaluated the mixing performance and is proposed as a practical numerical scheme for predicting the KSM behavior.     

The potential of serially coupled alkyl-bonded silica monolithic columns for high resolution separations of pharmaceutical compounds in biological fluids

Summary In this paper we investigate the potential of alkyl-bonded silica monolithic columns for the isolation and identification of drug-related components in biological fluids. Up to 6 columns have been connected in series to produce a chromatographic system with up to 40,000 plates. This high-resolution chromatography system has been coupled to both MS and NMR to enable efficient detection and characterisation of drug-related components in biological fluids. The use of six coupled columns has been shown to give enhanced resolution over a high quality silica particulate column packed with 3 μm material which exhibits the same back pressure. The effect of volume and mass load on the performance of monolithic columns for semi-preparative chromatography of biological fluids has also been investigated. In these studies it was possible to inject up to 100 mL of neat urine with no loss of chromatographic performance. Furthermore, upon re-testing, the columns showed similar chromatographic performance. Again several columns were serially connected, producing enhanced resolution in the semi-preparative mode.     

Evaluation of a sensitive HPLC method for the determination of Malondialdehyde, and application of the method to different biological materials

Summary Reactive oxygen species (ROS), important mediators of cell and tissue injury during inflammation, are produced by several types of inflammatory cells. The formation of ROS can be monitored by detection of lipid peroxidation products. The extremely broad spectrum of biological effects of aldehydic lipid peroxidation products has necessitated the development of a technique that enables the sensitive routine quantitation of aldehydes formed in biological materials. Malondialdehyde (MDA) is a by-product of enzymatic eicosanoid formation and an end-product of nonenzymatic peroxidation of polyunsaturated fatty acids with three or more bisallylic double bonds. The determination of the thiobarbituric acid derivative of MDA (TBA-MDA) is a widely used method for estimating overall lipid peroxidation. We describe a rapid, isocratic, simple, and sensitive high-performance liquid chromatographic (HPLC) method with spectrofluorimetric detection for measurement of MDA-TBA in human biological samples such as plasma, urine, wound secretions, amniotic fluid, sputum and tissue samples. By use of this method, picomole quantities of MDA can be readily and specifically detected in different biological materials. Coefficients of variation of repeated MDA-TBA assays were 4.4% within run and 6.9% from run to run. Reference values are given for a variety of human body fluids and for rat tissues.     

锂离子选择性微电极在生物体液中的响应

最近几年已报道了几种锂离子选择性电极.本文作者曾研制了以苯基膦酸二辛酯(DOPP)为溶剂,四苯硼酸盐为活性物质的PVC膜锂离子选择电极.本文在此基础上研制了锂离子选择性微电极,比较了以四苯硼酸钾(KTPB)及四苯硼酸钠(NaTPB)为活性物质的锂微电极的性能.同时考察了微电极在细胞内液、血清及生理盐液中对锂离子的响应特性.     

Simultaneous Determination of Aluminum and Iron in High Salt Content Matrices by Adsorptive Stripping Voltammetry. Application to Dialysis Fluids

A new analytical procedure for the simultaneous determination of aluminum(III) and iron(II) in two kinds of dialysis fluids (peritoneal and hemodialysis fluids) by differential pulse adsorptive stripping voltammetry (DPAdSV) is described. The voltammetric measurements were performed using, as working electrode, a stationary mercury electrode, and a platinum electrode and a Ag|AgCl|KCl_(sat.) electrode as auxiliary and reference electrodes, respectively, employing acetate buffer solutions at different pH as supporting electrolyte. As complexing agents, Solochrome Violet RS, Palatine Chrome Black 6BN, Chromazurol S and Eriochrome Black T were employed. For both elements, the accuracy, expressed as relative recovery R%, was very satisfactory being in the range 94–105%, the precision as repeatability, expressed as relative standard deviation s_r%, was lower than 6%, while the limits of detection were of the order of a few units of μg/L. The analytical voltammetric procedure has been validated by comparison with spectroscopic (graphite furnace atomic absorption spectroscopy, GFAAS) measurements.     

Chains in Critical Fluids and Nanopores

Summary: The conformational behavior of a polymer in a critical binary solvent confined in a porous medium is studied. The size of the polymer in bulk, which is mainly governed by the correlation length of the solvent density fluctuations, depends on the proximity to the critical point of the binary mixture. We find that in contrast to the bulk behavior, the conformational properties of the polymer in a porous medium depends strongly on the pore size. The latter controls the correlation length of the solvent density fluctuations and thus determines the polymer size.